Aminoresin based coatings containing 1,3,5-triazine tris-carbamate co-crosslinkers

ABSTRACT

An acid cured coating composition containing a hydroxyfunctional acrylic or polyester resin and a 1,3,5-triazine-2,4,6-tris-carbamate. Also provided is an acid cured coating composition containing a hydroxyfunctional acrylic or polyester resin, a crosslinking agent such as a melamine-formaldehyde or a related aminoresin, and a co-crosslinking agent derived from a triazine tris-carbamate such as 2,4,6-tris-(butoxycarbonylamino)-1,3,5-triazine. Also provided is an improved method of coating using the above coating compositions. The coating compositions described in this invention have lower cure temperatures, lower formaldehyde emissions during cure, and produce films and objects which have superior environmental etch resistance than the conventional melamine-formaldehyde coatings which do not have a triazine tris-carbamate co-crosslinker.

This application is a divisional of copending U.S. application Ser. No.07/998,313, filed Dec. 29, 1992.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to curable compositions containing polyfunctionalhydroxy group containing materials and a1,3,5-triazine-2,4,6-tris-carbamates. This invention also relates toaminoresin containing curable compositions which additionally contain a1,3,5-triazine-2,4,6-tris-carbamate derivative as a co-crosslinkingagent. Both compositions contain an acid cure catalyst.

2. Description of the Related Art

Aminoresin based coatings are well known in the art and have been usedfor nearly half a century in diverse applications including generalindustrial coatings, automotive coatings, coil coatings, powdercoatings, baking enamels, and wood finishes. Among the major drawbacksof aminoresin based coatings are formaldehyde emissions during cure andpoor environmental etch resistance of the cured coatings.

Alkyl and aryl 1,3,5-triazine-2,4,6-tris-carbamates and coatingsprepared therefrom have been described in a copending application Ser.No. 07/793,077 filed on Nov. 15, 1991; and in U.S. Pat. Nos. 5,084,541and 4,939,213. Coatings prepared by using1,3,5-triazine-2,4,6-tris-carbamate crosslinkers, although generallysatisfactory, are tin-catalyzed systems of high cost, requiringrelatively high bake temperatures to cure. They also yellow to someextent, in part due to the high bake temperatures required for cure.

It is the object of this invention to provide coatings which have theadvantages of melamine based systems such as low cost and low curetemperatures, and the advantages of 1,3,5-triazine,2,4,6-tris-carbamatebased systems such as good environmental etch resistance and absence offormaldehyde emissions during cure, without the drawbacks of eithersystem. Accordingly, described herein is a curable composition whichcomprises, as an additive to the commonly used aminoresin coatingcompositions, a 1,3,5-triazine-2,4,6-tris-carbamate co-crosslinkingagent. The novel curable compositions described herein have lowformaldehyde emissions when cured and have superior environmental etchresistance than the aminoresin based systems commonly used in thecoatings industry.

SUMMARY OF THE INVENTION

This invention is a curable composition, comprising:

(1) a polyfunctional hydroxy group containing material;

(2) a 1,3,5-triazine-2,4,6-tris-carbamate; and

(3) an acid cure catalyst.

This invention is also a curable composition, comprising:

(a) a polyfunctional hydroxy group containing material;

(b) an aminoresin crosslinking agent;

(c) a triazine tris-carbamate co-crosslinking agent; and

(d) an acid cure catalyst.

This invention is also an improved method of coating comprisingcontacting a substrate with the curable compositions of the inventionand thereafter heat curing.

The composition and the method of this invention have low curetemperatures and low formaldehyde emissions during cure. They alsoproduce films and objects which have superior environmental etchresistance than conventional aminoresin derived coatings.

DETAILED DESCRIPTION

We have discovered, surprisingly, that when a carbamate co-crosslinkingagent is added to conventional aminoresin based coating compositions,three of the major deficiencies of the aminoresin and tris-carbamatebased coatings are overcome:

(1) the cure temperatures of the tris-carbamate derived compositions arelowered by using an acid catalyst instead of a tin catalyst or nocatalyst at all;

(2) the high formaldehyde emissions normally encountered in aminoresinderived curable compositions during cure are reduced to lower levels;and

(3) coatings produced from curable compositions containing a carbamateco-crosslinking agent have superior environmental etch resistance whencompared with conventional aminoresin coatings.

This invention is a curable composition comprising:

(1) a polyfunctional hydroxy group containing compound;

(2) a 1,3,5-triazine-2,4,6-tris-carbamate; and

(3) an acid cure catalyst.

The above composition is characterized by the use of an acid curecatalyst instead of a tin catalyst described in U.S. Pat. Nos. 5,084,541and 4,939,213. Compositions described in the cited patents are notsuitable for use in coatings when the curable composition additionallycontains an aminoresin crosslinking agent. In contrast, the curablecompositions described herein may additionally contain an aminoresin andproduce, upon cure, superior coatings.

This invention, therefore, is also a curable composition, comprising:

(a) a polyfunctional hydroxy group containing material;

(b) an aminoresin crosslinking agent;

(c) a carbamate co-crosslinking agent; and

(d) a cure catalyst.

The curable compositions of this invention have utility in coatings,such as general industrial coatings, automotive coatings, coil coatings,powder coatings, baked enamels, and wood finishes. They are also usableas molding and adhesive compositions.

The aminoresin containing curable compositions of the inventioncomprise:

(a) a polyfunctional hydroxy group containing material;

(b) an aminoresin crosslinking agent;

(c) a carbamate co-crosslinking agent selected from the group consistingof:

(i) a 1,3,5-triazine-2,4,6-tris-carbamate of the formula C₃ N₃(NHCOOR)₃, wherein R in each NHCOOR group is independently selected fromthe group consisting of an alkyl of 1 to 20 carbon atoms, an aryl of 6to 20 carbon atoms, an aralkyl of 7 to 20 carbon atoms, and a mixturethereof;

(ii) an oligomer of (i); and

(iii) a mixture of (i) and (ii); and

(d) an acid cure catalyst.

These compositions are described in greater detail below.

POLYFUNCTIONAL MATERIALS

The polyfunctional hydroxy group containing materials usable in thecurable compositions of the invention are those conventionally used inaminoresin coatings and are capable of reacting with both aminoresincrosslinking agents and with carbamate co-crosslinking agents.

Suitable polyfunctional hydroxy group containing materials includepolyols, hydroxyfunctional acrylic resins containing pendant or terminalhydroxy functionalities, hydroxyfunctional polyester resins containingpendant or terminal hydroxy functionalities, hydroxyfunctionalpolyurethane prepolymers, products derived from condensation of epoxyresins with an amine, and a mixture thereof.

Acrylic and polyester resins are preferred.

An example of a suitable polyfunctional acrylic resin availablecommercially from S. C. Johnson & Sons, Inc., is JONCRYL® 500 acrylicresin, comprising a copolymer of styrene (50%), hydroxypropylmethacrylate (20%) and butyl acrylate (30%) having the followingproperties:

Solids Content: (%) 80

Hydroxyl Number (based on solids): 140

Equivalent Weight (based on solids): 400

Viscosity (Centipoise): 4,000

Molecular Weight, Number Average: 1,300

Molecular Weight, Weight Average: 2,210

Polydispersity: 1.7

A similar resin is also available from Rohm & Haas under the trademarkAT-400.

Other examples of suitable polyfunctional hydroxy group containingmaterials include commercially available polyester resins such asCYPLEX® 1531, a polyester of phthalic acid, adipic acid, ethanediol, andtrimethylolpropane, a product of Cytec Industries, West Paterson, N.J.;CARGIL POLYESTER 5776 available from Cargill Corporation; TONE®polylactone resins available from Union Carbide Corporation; K-FLEX®XM-2302 and XM-2306, a product of King Industries, Norwalk, Conn.; andCHEMPOL® 11-1369, a product of Cook Composites and Polymers, PortWashington, Wis.

AMINORESIN CROSSLINKING AGENTS

The aminoresin crosslinking agents usable in the curable compositions ofthe invention are partially or fully methylolated, substantially fullyetherified amino compounds such as melamine, glycoluril, guanamine, andurea. They may be monomeric or oligomeric, the oligomeric forms arisingfrom the self condensation of the monomeric forms under acidicconditions, and particularly under acidic conditions at super ambienttemperatures. The aminoresin crosslinking agents of the invention arefurther characterized by having at least 2, and preferably more than 2crosslinkingly reactive groups such as alkyoxymethyl groups percrosslinker molecule.

The aminoresin crosslinking agents usable in the curable compositions ofthe invention are exemplified further hereinbelow:

Melamine-based aminoresin crosslinking agents are well known in the artand have been used extensively as effective crosslinkers in coatings.The alkoxymethylmelamine functionality can be a maximum of six in acrosslinkingly effective range of 2 to 6 alkoxymethyl groups per eachmelamine molecule. In addition to monomers, alkoxymethyl melamines cancontain dimers, trimers, tetramers, and higher oligomers, each givencombination of comonomers and oligomers being preferred for a givenapplication. For example, the lower viscosity monomer-rich compositionsare preferred for solvent-based high solids coatings.

An example of the substantially fully etherified, substantially fullymethylolated, substantially monomeric melamines usable in this inventionis CYMEL® 303 melamine crosslinking agent, a product of CytecIndustries, West Paterson, N.J., having the following physical andchemical properties:

Non-Volatiles (% by weight)*: 98

Color, Maximum (Gardner 1963): 1

Viscosity (Gardner-Holt, at 25° C.): X-Z

Free Formaldehyde, maximum (weight %): 0.5

Degree of Polymerization: 1.75

An example of a partially methylolated, substantially fully etherifiedpartially oligomeric melamine-formaldehyde resin is CYMEL® 323 melaminecrosslinking agent, a product of Cytec Industries, West Paterson, N.J.,having the following properties:

Principal Reactive Group: NHCH₂ OCH₃

Solvent: Isobutanol

Degree of Polymerization*: 2.2

Non-Volatiles (% by weight**): 80±2

Viscosity (Gardner-Holt, at 25° C.): Y-Z₃

Viscosity (Poise, approximate): 30-71

An example of the substantially fully etherified, substantially fullymethylolated, substantially monomeric mixed alkyl melamines is CYMEL®1168 melamine crosslinking agent, a product of Cytec Industries, WestPaterson, N.J. The alkyl group in CYMEL® 1168 consists essentially of amixture of methyl and isobutyl groups. It has the following properties:

Non-Volatiles (% by weight)*: 98

Color, Maximum (Gardner 1963): 1

Viscosity (Gardner-Holt, at 25° C.): X-Z

Free Formaldehyde, maximum (weight %): 0.5

Equivalent Weight: 150-230

An example of a substantially methylolated, partially etherified,substantially oligomeric melamine is CYMEL® 370 crosslinking agent, aproduct of Cytec Industries, West Paterson, N.J. It has the followingproperties:

Non-Volatiles (% by weight)*: 88±2

Solvent: Isobutanol

Color, Maximum (Gardner 1963): 1

Viscosity (Gardner-Holt, at 25° C.): Z₂ -Z₄

Equivalent Weight: 225-325

The preferred glycoluril crosslinkers of this invention areN-alkoxymethyl substituted glycolurils wherein at least two of the alkylgroups in the alkoxymethyls are selected from a group consisting ofmethoxymethyl, ethoxymethyl, propoxymethyl, butoxymethyl, pentoxymethyl,hexoxymethyl, heptoxymethyl, octoxymethyl, nonoxymethyl, decoxymethyland mixtures thereof, and the remaining alkyl groups are selected fromhydrogen, alkyl, hydroxymethyl, and glycoluril group-containingoligomeric moieties.

While it is preferable to have 4 alkoxymethyl groups per each glycolurilcrosslinking agent, under ordinary circumstances it may not be necessaryto obtain the pure tetrasubstituted monomeric crosslinkerN,N',N",N"'-tetraalkoxymethylglycolurils, so that resinous materials arenormally usable.

The monomeric tetraalkoxyglycolurils themselves are not considered to beresinuous materials since they are, as individual entities,non-polymeric compounds. They are considered, however, to be potentialresin-forming compounds when subjected to heat, and particularly whensubjected to heat under acidic conditions. As a result of the describedresin-forming ability, the substantially monomeric glycolurilcrosslinkers of this invention may contain some higher oligomericcomponents such as dimers, trimers, and tetramers. The presence ofmodest amounts of these oligomeric forms is permissible and indeedbeneficial in cases where a high melting solid crosslinker is desirableas it is the case in powder coatings.

An example of glycoluril crosslinker of this invention is POWDERLINK®1174 Powder Crosslinking Agent, a product of Cytec Industries, WestPaterson, N.J., and has the following properties:

Non-Volatiles, minimum (% by weight): 98

Appearance: White to pale yellow granulated flakes

Melting Point (°C.): 90°-110° C.

Average Molecular Weight: 350

Equivalent Weight : 90-125

Another example of a glycoluril crosslinker of this invention is CYMEL®1170 fully butylated glycoluril crosslinker, a product of CytecIndustries, West Paterson, N.J., having the following properties:

Non-Volatiles, minimum (% by weight): 95

Appearance: Clear liquid

Color, Maximum (Gardner, 1963): 3

Viscosity (Gardner-Holt, 25° C.): X-Z₂

Molecular Weight, Average: 550

Equivalent Weight: 150-230

Methylol Content: Very low

As in melamines, the partially or fully methylolated or etherified alkyland aryl guanamine aminoresins, both in their monomeric and oligomericforms, are usable as crosslinking agents in this invention, with theselection depending on the particular application or the propertiesdesired in the product.

Benzoguanamine, cyclohexylcarboguanamine and acetoguanamine aminoresinsare especially preferred as crosslinkers in this invention.

An example of a benzoguanamine-based crosslinking agent is CYMEL® 1123resin, a product of Cytec Industries, West Paterson, N.J., wherein thealkyl in the alkoxymethyls is a mixture of methyl and ethyl groups.

An example of a urea crosslinker usable in this invention is BEETLE® 80butylated urea formaldehyde resin, a product of Cytec Industries, WestPaterson, N.J., having the following properties:

Non-Volatiles (% by weight)*: 96±2

Solvent Tolerance (ASTM D1198-55): >500

Color, Maximum (Gardner 1963): 1

Viscosity (Gardner-Holt, at 25° C.): X-Z₂

It is evident from the discussions above, that a person skilled in theart, in selecting the most suitable crosslinker for a particularapplication, may choose a mixture thereof which imparts a balance ofproperties desired for that particular application.

CARBAMATE CO-CROSSLINKING AGENTS

The carbamate co-crosslinking agents usable in the curable compositionsof the invention are 1,3,5-triazine-2,4,6-tris-carbamates having thefollowing formula:

    C.sub.3 N.sub.3 (NHCOOR).sub.3

wherein R in each NHCOOR group is independently selected from the groupconsisting of an alkyl of 1 to 20 carbon atoms, an aryl of 6 to 20carbon atoms, an aralkyl of 7 to 20 carbon atoms, and a mixture thereof.

The preferred carbamate co-crosslinking agents are carbamates whereinthe R group is an alkyl group of 1 to 8 carbon atoms. Particularlypreferred are 2,4,6-tris-(methoxycarbonylamino)-1,3,5-triazinerepresented by the formula:

    C.sub.3 N.sub.3 (NHCOOCH.sub.3).sub.3

and 2,4,6-tris-(butoxycarbonylamino)-1,3,5-triazine represented by theformula:

    C.sub.3 N.sub.3 (NHCOOCH.sub.2 CH.sub.2 CH.sub.CH.sub.3).sub.3

and a mixture thereof.

The carbamate co-crosslinking agents may be prepared by proceduresdescribed in a copending application Ser. No. 07/793,077 filed on11/5/91, and in U.S. Pat. Nos. 5,084,541 and 4,939,213, the contents ofwhich are incorporated herein by reference.

CURE CATALYSTS

As set forth herein, the curable composition optionally also includes acure catalyst. As is recognized in U.S. Pat. Nos. 5,084,541 and4,939,213, a tin catalyst is typically required when a curablecomposition contains a 1,3,5-triazine-tris-carbamate derivative as thesole crosslinking agent. Uncatalyzed or acid catalyzed curablecompositions containing 1,3,5-triazine-2,4,6-tris-carbamate derivativesremain hitherto unreported.

It is the discovery of this invention to provide acid catalyzed curablecompositions capable of simultaneous cure by the aminoresin crosslinkersand the 1,3,5-triazine-triscarbamate co-crosslinkers present therein.

The cure catalysts usable in the curable compositions of the inventioninclude sulfonic acids, aryl and alkyl acid phosphates andpyrophosphates, carboxylic acids, sulfonimides, mineral acids, andmixtures thereof. Of the above acids, sulfonic acids are preferred.Examples of sulfonic acids include benzenesulfonic acid,para-toluenesulfonic acid, dodecylbenzenesulfonic acid,naphthalenesulfonic acid, dinonylnaphthalenedisulfonic acid, and amixture thereof. Examples of the dialkyl acid pyrophosphates includephenyl, methyl, ethyl, diphenyl, dimethyl and diethyl acid phosphatesand pyrophosphates. Examples of carboxylic acids include benzoic acid,propionic acid, butyric acid, formic acid, oxalic acid, trifiuoroaceticacid, and the like. Examples of the sulfonimides includedibenzenesulfonimide, di-para-toluenesulfonimide,methyl-para-toluenesulfonimide, dimethylsulfonimide, and the like.Examples of the mineral acids include nitric acid, sulfuric acid,phosphoric acid, polyphosphoric acid, and the like.

RATIO AND PROPORTIONS OF THE INGREDIENTS

In the practice of the invention, a crosslinkingly effective amount ofan aminoresin crosslinking agent and a 1,3,5-triazine2,4,6-tris-carbamate co-crosslinking agent is used. It is desirable tocrosslink at least one half of the hydroxy functionalities present inthe polyfunctional hydroxy group containing material to obtain coatingsof good physical and resistance properties. It is preferred, however,that the mole ratio of the hydroxy groups to the sum of thecrosslinkingly effective functionalities present in the aminoresincrosslinking agent and the 1,3,5-triazine 2,4,6-triazine tris-carbamateco-crosslinking agent is in the range of from 0.8:1 to 1.2.:1.

The weight ratio of the aminoresin crosslinking agent to the carbamateco-crosslinking agent usable in the curable composition of the inventionare typically in the range of from 99:1 to 0.2:1. The weight ratio ofthe polyfunctional hydroxy group containing material to the sum of theaminoresin crosslinking agent and the carbamate co-crosslinking agent isin the range of from 99:1 to 0.5:1. The weight percent of the acid curecatalyst to the sum of the polyfunctional hydroxy group Containingmaterial, the aminoresin crosslinking agent, and the carbamateco-crosslinking agent is in the range of from 0.01 weight percent to 3weight percent.

OPTIONAL INGREDIENTS

The optional ingredients present in the curable composition of theinvention vary depending on the intended use of the cured article orfilm.

Suitable optional ingredients include fillers, ultraviolet lightstabilizers, pigments, flow control agent, plasticizers, mold releaseagents, and corrosion inhibitors.

The composition of the invention may contain as an optional ingredient aliquid medium. Such a medium may be used to aid the uniform applicationand transport of the curable composition. Any or all of the ingredientsof the composition may be contacted with the liquid medium. Moreover,the liquid medium may permit formation of a dispersion, emulsion, invertemulsion, or solution of the curable composition ingredients.Particularly preferred is a liquid medium which is a solvent for thecurable composition ingredients (a), (b), (c), and (d). Suitablesolvents are selected from alcohols, ketones, ethers, esters, water,aliphatic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbonsand mixtures thereof.

IMPROVED METHOD OF COATING

Another aspect of this invention is an improved method of coating orsubstrate said method being of the type having the steps of contacting asubstrate with a curable composition containing a polyfunctional hydroxygroup containing material and a 1,3,5-triazine-2,4,6-trisocarbamate, andthereafter heat curing said curable composition, wherein the improvementcomprises:

(A) contacting said substrate with a curable composition, comprising:

(1) a polyfunctional hydroxy group containing material;

(2) a 1,3,5-triazine-2,4,6-tris-carbamate; and

(3) an acid cure catalyst; and thereafter

(B) heat curing said curable composition to produce a crosslinked filmor object.

Another method of this invention is an improved method of coating asubstrate, said method being of the type having the steps of contactingsaid substrate with a curable composition containing a polyfunctionalhydroxy group containing material, an aminoresin crosslinking agent, andan acid cure catalyst, and thereafter heat curing said curablecomposition, wherein the improvement comprises:

(C) contacting said substrate with a curable composition, comprising:

(1) a polyfunctional hydroxy group containing material;

(2) an aminoresin crosslinking agent;

(3) a carbamate co-crosslinking agent selected from the group consistingof:

(i) a 1,3,5-triazine tris-carbamate of the formula C₃ N₃ (NHCOOR)₃,wherein R in each NHCOOR group is independently selected from the groupconsisting of an alkyl of 1 to 20 carbon atoms, an aryl of 6 to 20carbon atoms, an aralkyl of 7 to 20 carbon atoms, and a mixture thereof;

(ii) an oligomer of (i); and

(iii) a mixture of (i) and (ii); and

(D) heat curing said curable composition to produce a crosslinked filmor object.

In the practice of the methods of the invention, the curablecompositions of the invention containing the 1,3,5-triazine2,4,6-tris-carbamate co-crosslinkers are typically formulated as aliquid paint and applied onto a substrate by a method such as padding,brushing, rollercoating, curtain coating, flowcoating, electrostaticspraying, electrocoating or dipping. The coated substrate thereafter isheat cured at a temperature typically in the range of from 90° C. toabout 140° C. to effect crosslinking and producing cured films orobjects.

For powder coating applications, solid ingredients and highertemperatures in the range of 175° C. to 190° C. are typically used."Powder coating" is an art recognized coating process and is definedherein as a method of electrostatic powder spraying wherein a finelydivided solid coating material is electrostatically attracted to asurface of an article. Alternatively, the powder coating composition maybe contacted with the substrate by immersing the substrate in fluidizedbed of powder. The article covered with the powder is heated to at leastthe fusion temperature of the coating composition forcing it to flow outand form a coating which is cured by further application of heat.

For coil coating applications, temperatures typically in the range of180° C. to 360° C. are used to cure.

CROSSLINKED ARTICLES AND COATINGS FORMED BY THE COMPOSITIONS OF THISINVENTION

The curable compositions of this invention containing the carbamateco-crosslinkers of the invention can be heat cured (typically 90° C. to140° C.) to produce crosslinked moulded articles, adhesives andcoatings. Because of the polyfunctional nature of the reactants, theresulting product in this case is a crosslinked article in the form of afilm such as adhesives or coatings or in the form of an article such asmolded products and objects.

The heat-cured compositions of this invention may be employed ascoatings for wire, appliances, automotive parts, furniture, pipes,machinery, and the like. Suitable surfaces include glass, plastics, woodand metals such as steel, and aluminum.

The heat-cured compositions may also be used to form solid articles suchas cases, enclosures, and structural members.

The following Examples illustrate various embodiments of the invention.

EXAMPLE 1 PREPARATION OF ACRYLIC COPOLYMER A

The polyfunctional hydroxy group containing material ACRYLIC COPOLYMER Awas prepared as follows:

COPOLYMER A was prepared by admixing COPOLYMER B (70.2 g), COPOLYMERC(63.5 g), and normal butyl acetate (13.3 g).

PREPARATION OF COPOLYMER B

A first stream of a solution containing tertiary butyl peroctoate (28.94g), tertiary amyl perbenzoate (5.11 g), and meta-xylene (11.35 g) and asecond stream of a solution containing methyl methacrylate (231.9 g),styrene (62.6 g), normal butyl acrylate (27.5 g), and hydroxyethylacrylate (178.8 g) were simultaneously introduced, over a period of 5hours, into a flask containing meta-xylene (305 g) at 138° C. to 140° C.After heating at 140° C. for an additional 3 hours, a portion of thevolatiles (about 85 g) was removed to give COPOLYMER B having thefollowing properties:

% Solids: 71.2

% Hydroxide: 3.58

Molecular Weight:

Number Average: 4,000

Weight Average: 7,900

Polydispersity: 1.97

Glass Transition (Tg)

By DMA (°C.): 57±2

By DSC (°C.): 38±1

PREPARATION OF COPOLYMER C

The procedure for preparation of COPOLYMER B was repeated with thefollowing changes:

FIRST STREAM:

TRIGONOX 29-B75 Initiator (g): 38.56

Meta Xylene (g): 12.86

SECOND STREAM:

Methyl Methacrylate (g): 232.3

Normal Butyl Acrylate (g): 101.4

Hydroxyethyl Methacrylate (g): 165.8

Meta Xylene in the Flask (g): 202.7

The product formed was COPOLYMER C having the following properties:

% Solids: 78.7

% Hydroxide: 3.19

Molecular Weight:

Number Average: 3,900

Weight Average: 8,600

Polydispersity: 2.20

Glass Transition (Tg)

By DMA (°C.): 40±1

By DSC (°C.): 22±1

EXAMPLE 2

Three coatings derived from a composition containing thehydroxyfunctional acrylic resin COPOLYMER A of EXAMPLE 1 and2,4,6-tris-(butoxycarbonylamino)-1,3,5-triazine were heat-cured with:

(1) para-toluenesulfonic acid (COATING A)

(2) dimethyl tin dilaurate (COATING B)

(3) no catalyst (COATING C)

The coatings were formulated, applied onto base-coated panels and curedas follows:

    ______________________________________                                                          COATING                                                                       A      B      C                                             ______________________________________                                        ACRYLIC COPOLYMER A OF                                                                            73.3     73.3   73.3                                      EXAMPLE 1 (g):                                                                2,4,6-tris-(Butoxycarbonylamino)-                                                                 26.7     26.7   26.7                                      1,3,5-triazine (g):                                                           Catalyst:                                                                     (1) para-Toluenesulfonic acid (g):                                                                 0.5     --     --                                        (2) Dimethyl Tin Dilaurate (g):                                                                   --        0.5   --                                        (3) No Catalyst:    --       --      0.0                                      Substrate, White Base-Coated Panels:                                          ED-11 CRS*                                                                    Cure Schedule                                                                 (Table 1): 125° C./30 min.                                             (Table 2): 125° C./30 min.                                             ______________________________________                                         *ED-11 primed cold rolled steel (CRS) is a product of Advanced Coating        Technologies, Inc., Hillsdale, MI.                                       

The cured coatings A, B, and C were thereafter analyzed for performance.The results are summarized in Table 1 for 125° C./30 min. cure scheduleand in Table 2 for 135° C./30 min. cure schedule coatings.

                  TABLE 1                                                         ______________________________________                                        SOLVENT RESISTANCE* OF 2,4,6-TRIS-                                            (BUTOXYCARBONYLAMINO)-1,3,5-TRIAZINE                                          CONTAINING COMPOSITIONS IN ACID CATALYZED,                                    TIN CATALYZED, AND UNCATALYZED COATINGS                                       CURED AT 125° C./30 MINUTES SCHEDULES                                             COATING  COATING   COATING                                                    A        B         C                                               ______________________________________                                        Thickness                                                                     (mils)        1.8        1.8       1.9                                        (mm)           0.046      0.046     0.048                                     Hardness                                                                      KHN.sub.25   12.4       12.5      12.4                                        Pencil       H-2H       H-2H      H-2H                                        Methyl Ethyl Ketone                                                           Rubs to Mar  200+       200       100                                         to Remove    200+       200+      200+                                        Yellow Index,                                                                 Original     -3.9       -3.9      -4.0                                        After 1st 30 min                                                                           -3.9       -3.9      -4.0                                        Overbake                                                                      After 2nd 30 min.                                                                          -3.8       -3.8      -3.9                                        Overbake                                                                      ______________________________________                                         *Solvent Resistance is measured by Methyl Ethyl Ketone (MEK) Double Rubs      "to mar" or "to remove" the coating. Highly crosslinked coatings require      200+ (i.e. more than 200) MEK Rubs to mar.                               

                  TABLE 2                                                         ______________________________________                                        SOLVENT RESISTANCE* OF 2,4,6-TRIS-                                            (BUTOXYCARBONYLAMINO)-1,3,5-TRIAZINE                                          CONTAINING COMPOSITIONS IN ACID CATALYZED,                                    TIN CATALYZED, AND UNCATALYZED COATINGS                                       CURED AT 135° C./30 MINUTES SCHEDULES                                             COATING  COATING   COATING                                                    A        B         C                                               ______________________________________                                        Thickness                                                                     (mils)        1.8        1.9       1.8                                        (mm)           0.046      0.048     0.046                                     Hardness                                                                      KHN.sub.25   14.4       13.2      13.4                                        Pencil       H-2H       H-2H      H-2H                                        Methyl Ethyl Ketone                                                           Rubs to Mar  200+       150       100                                         to Remove    200+       200+      200+                                        Yellow Index,                                                                 Original     -2.3       -2.4      -2.4                                        After 1st 30 min                                                                           -2.0       -2.0      -2.0                                        Overbake                                                                      After 2nd 30 min.                                                                          -1.7       -1.9      -1.8                                        Overbake                                                                      ______________________________________                                         *Solvent Resistance is measured by Methyl Ethyl Ketone (MEK) Double Rubs      "to mar" or "to remove" the coating. Highly crosslinked coatings require      200+ (i.e. more than 200) MEK Rubs to mar.                               

EXAMPLE 3

A coating prepared using the curable composition of the invention,COATING D, was compared with a conventional aminoresin coating, COATINGE.

COATING D and COATING E were formulated, applied onto base-coated panelsand cured as follows:

    ______________________________________                                                       COATING D COATING E                                            ______________________________________                                        Acrylic COPOLYMER A of                                                                         73.3        73.3                                             EXAMPLE 1 (g):                                                                CYMEL ® 303 Aminoresin                                                                     13.4        26.7                                             Crosslinker:                                                                  2,4,6-tris-      13.4         0.0                                             (Butoxycarbonylamino)-                                                        1,3,5-triazine (g):                                                           para-Toluenesulfonic Acid (g):                                                                  0.4         0.4                                             Substrate, White Base-Coated                                                                   ED-11CRS    ED-11CRS                                         Panels:                                                                       Cure Schedule (Table 3):                                                                       125° C./30 min                                                                     125° C./30 min                            ______________________________________                                         The cured coatings were thereafter analyzed for performance. The results      are summarized in Table 3.                                               

                  TABLE 3                                                         ______________________________________                                        PHYSICAL AND RESISTANCE PROPERTIES OF                                         COATING D AND COATING E                                                                        COATING COATING                                                               D       E                                                    ______________________________________                                        Thickness                                                                     (mils)              1.8       1.8                                             (mm)                 0.046     0.046                                          Hardness                                                                      KHN.sub.25         13.1      13.3                                             Pencil             H-2H      H-2H                                             Methyl Ethyl Ketone                                                           Rubs, to Mar       200+      200+                                             Adhesion, Top Coat to Base Coat                                                                  5         5                                                Yellow Index,                                                                 Original           -4.5      -4.7                                             After 1st 30 min Overbake                                                                        -4.4      -4.7                                             After 2nd 30 min Overbake                                                                        -4.3      -4.6                                             Xenon Weathering, 1585 Hours,                                                 Yellow Index        2.5       3.0                                             Gloss 20°/60°                                                                      69/83     67/84                                            ______________________________________                                    

EXAMPLE 4

The experiment in EXAMPLE 3 was repeated with the exception that insteadof CYMEL® 303 resin, high imino group containing CYMEL® 323 resin wasused and instead of the para-toluenesulfonic acid catalyst, somewhatweaker dimethyl acid pyrophosphate cure catalyst was used. Thus, COATINGF contained both an aminoresin crosslinker and a tris-carbamateco-crosslinker, whereas COATING G contained only the aminoresincrosslinker for comparison.

The cured coatings were thereafter analyzed for performance. The resultsare summarized in Table 4.

                  TABLE 4                                                         ______________________________________                                        PHYSICAL AND RESISTANCE PROPERTIES OF                                         COATING F AND COATING G                                                                        COATING COATING                                                               F       G                                                    ______________________________________                                        Thickness                                                                     (mils)              1.7       1.6                                             (mm)                 0.043     0.041                                          Hardness                                                                      KHN.sub.25         12.5      13.9                                             Pencil             H-2H      H-2H                                             Methyl Ethyl Ketone                                                           Rubs to Mar        200+      200+                                             to Remove          200+      200+                                             Adhesion, Top Coat to Base Coat                                                                  5         3                                                Yellow Index,                                                                 Original           -4.2      -4.4                                             After 1st 30 min Overbake                                                                        -4.2      -4.4                                             After 2nd 30 min Overbake                                                                        -4.1      -4.2                                             Xenon Weathering, 1585 Hours,                                                 Yellow Index       -2.8      -3.6                                             Gloss 20°/60°                                                                      75/87     66/83                                            ______________________________________                                    

EXAMPLE 5

The environmental etch resistance of COATINGS D, E, F, and G wasdetermined as follows:

2 drops of an acid was added to the surface of a coating at roomtemperature and thereafter heated to 50° C. for 20 minutes. Then, theappearance of the coating was examined visually and the changes noted.

COATINGS D, E, F, and G were tested for environmental etch resistance asdescribed above using:

(a) aqueous sulfuric acid (0.1 Normal); or

(b) aqueous phosphoric acid (0.1 Normal).

The results using sulfuric acid are summarized in Table 5 and thoseusing phosphoric acid are summarized in Table 6.

                  TABLE 5                                                         ______________________________________                                        ENVIRONMENTAL ETCH RESISTANCE OF                                              COATINGS D, E, F, AND G USING 0.1                                             NORMAL SULFURIC ACID                                                          COATING    TEST RESULTS                                                       ______________________________________                                        D          Contact area swelled                                               E          Contact area etched down to base coat                              F          Contact area swelled                                               G          Contact area swelled and severely cracked                          ______________________________________                                    

                  TABLE 6                                                         ______________________________________                                        ENVIRONMENTAL ETCH RESISTANCE OF                                              COATINGS D, E, F, AND G USING 0.1                                             NORMAL PHOSPHORIC ACID                                                        COATING    TEST RESULTS                                                       ______________________________________                                        D          Contact area swelled                                               E          Contact area was partially etched away                             F          Contact area swelled                                               G          Contact area swelled and severely cracked                          ______________________________________                                    

EXAMPLE 6

A coating using the curable composition of the invention, COATING H, wascompared with a conventional aminoresin, COATING I.

COATING H and COATING I were formulated, applied onto base-coatedpanels, and cured. The formulations comprise the following:

    ______________________________________                                                       COATING H COATING I                                            ______________________________________                                        TA 39-14 Acrylic resin* (g):                                                                   72          65                                               CYMEL ® 1170 14          35                                               Crosslinker (g):                                                              2,4,6-tris-      14           0                                               (Butoxycarbonylamino)-                                                        1,3,5-triazine (g):                                                           para-Toluenesulfonic Acid (g):                                                                   0.6         0.6                                            Substrate, White Base-Coated                                                                   ED-11 CRS   ED-11CRS                                         Panels:                                                                       Cure Schedule:   125° C./30 min                                                                     125° C./30 min                            ______________________________________                                         *TA 3914 Acrylic Resin is a product of Dock Resins Corp., Linden, N.J.        having an equivalent weight of 450.                                      

The cured coating were thereafter analyzed for performance. The resultsare summarized in TABLE 7.

                  TABLE 7                                                         ______________________________________                                                         COATING COATING                                                               H       I                                                    ______________________________________                                        Thickness                                                                     (mils)              1.88      1.65                                            (mm)                 0.048     0.042                                          Hardness                                                                      KHN.sub.25          5.7       4.2                                             Pencil             H-2H      F-H                                              Methyl Ethyl Ketone                                                           Rubs to Mar        200+      200+                                             Adhesion, Top Coat to Base Coat                                                                  5         3                                                Yellow Index,                                                                 Original           -1.8      -1.9                                             After 1st 30 min Overbake                                                                        -1.1      -1.1                                             After 2nd 30 min Overbake                                                                        -0.9      -1.0                                             Gloss 20°/60°, Original                                                            86/93     85/93                                            ______________________________________                                    

EXAMPLE 7

The procedure of EXAMPLE 5 was repeated using COATING H and COATING I.The results are summarized in TABLE 8 (sulfuric acid) and TABLE 9(phosphoric acid).

                  TABLE 8                                                         ______________________________________                                        ENVIRONMENTAL ETCH RESISTANCE OF                                              COATING H AND COATING I                                                       USING 0.1 NORMAL SULFURIC ACID                                                COATING TEST RESULTS                                                          ______________________________________                                        H       Contact area swelled in rings                                         I       Contact area severely swollen and slightly cracked                    ______________________________________                                    

                  TABLE 9                                                         ______________________________________                                        ENVIRONMENTAL ETCH RESISTANCE OF                                              COATING H AND COATING I                                                       USING 0.1 NORMAL PHOSPHORIC ACID                                              COATING       TEST RESULTS                                                    ______________________________________                                        H             Contact area was slightly swollen                               I             Contact area was swollen                                        ______________________________________                                    

EXAMPLE 8

The procedure of EXAMPLE 3 was repeated using a different acrylic resin,different ratios of CYMEL® 303 crosslinker and2,4,6-tris-(butoxycarbonylamino)-1,3,5-triazine co-crosslinker toprepare COATINGS J, K, L, M, and N. The coatings were formulated,applied onto base-coated panels, and cured. The formulations comprisethe following:

    ______________________________________                                                      COATINGS                                                                      J     K      L      M    N                                      ______________________________________                                        TA 39-14 Acrylic Resin (g)                                                                    7.80    77.5   72.2 76.5 78.2                                 CYMEL ® 303 Crosslinker                                                                   19.8    14.6   11.4 4.7  21.8                                 2,4,6-tris-     2.2     7.9    11.4 18.8 0.0                                  (Butoxycarbonylamino)-                                                        1,3,5-triazine                                                                para-Toluenesulfonic acid                                                                     0.4     0.4    0.4  0.4  0.4                                  ______________________________________                                         Substrate, White BaseCoated Panels ED11CRS                                    Cure Schedule: 125° C./30 min                                     

                  TABLE 10                                                        ______________________________________                                        PHYSICAL AND RESISTANCE PROPERTIES OF                                         COATINGS J, K, L, M AND N                                                                COATINGS                                                                      J     K       L       M     N                                      ______________________________________                                        Thickness                                                                     (mils)       1.77    1.65    1.75  1.73  1.75                                 (mm)         0.045   0.042   0.044 0.044 0.044                                Hardness,                                                                     KHN.sub.25   5.9     5.8     5.8   6.1   5.9                                  Pencil       F-H     F-H     F-H   F-H   B-HB                                 Methyl Ethyl Ketone                                                           Rubs, to Mar 200+    200+    200+  200+  200+                                 Adhesion, Top Coat to                                                                      5       5       5     5     2-3                                  Base Coat                                                                     Gloss 20°/60°,                                                               86/93   86/93   87/94 86/93 86/93                                Original                                                                      Yellow Index,                                                                 Original     -2.4    -2.7    -2.1  -2.3  -2.5                                 After 1st Overbake                                                                         -1.8    -2.2    -1.6  -1.7  -1.9                                 After 2nd Overbake                                                                         -1.7    -2.1    -1.4  -1.6  -1.7                                 Chip Resistance*                                                                           5       5-6     5     4-5   5-6                                  ______________________________________                                         *Chip Resistance scale: 0 is the best, 10 is the worst.                  

EXAMPLE 9

The procedure of EXAMPLE 8 used to prepare COATING L and COATING N wasrepeated to prepare COATING O and COATING P, respectively, with theexception that the base coat and the primer were omitted, and the baketemperature was 135° C./30 min.

Coated coupons, enclosed in a glass chamber having humid air blowntherethrough at a rate of 50 ml per minute, were heated at 135° C. for30 minutes to cure the coatings. The released formaldehyde was collectedand analyzed by a procedure described in an article by J. McClure inAnalytical Le Hers, Volume 21, Number 2, page 253 (1988), the contentsof which are incorporated herein by reference. The results aresummarized in Table 11.

                  TABLE 11                                                        ______________________________________                                        FORMALDEHYDE EMISSIONS OF COATING L                                           AND COATING N DURING CURE                                                                    COATING L                                                                              COATING N                                             ______________________________________                                        THICKNESS,                                                                    (mils)           1.2        1.2                                               (mm)              0.030      0.030                                            HARDNESS, KHN.sub.25                                                                           7.2        8.6                                               FORMALDEHYDE (%)*                                                                              1.0        2.0                                               ______________________________________                                         *Emitted formaldehyde, based on dry film weight.                         

EXAMPLE 10

The procedure of EXAMPLE 3 was repeated using a formulation comprising apolyester resin instead of an acrylic resin. Further, a portion of thepolyester was ground, in a three roll mill with titanium dioxide pigmentand thereafter the remaining ingredients were added. COATING Q, COATINGR, and COATING S were prepared as before by curing at 125° C. for 30minutes.

The ingredients comprising the formulations and the physical andresistance properties of the cured coatings are summarized in TABLE 12.

                  TABLE 12                                                        ______________________________________                                        COATING PERFORMANCE OF COATINGS                                               Q, R, AND S                                                                   IN A PIGMENTED POLYESTER SYSTEM                                                            COATING COATING   COATING                                                     Q       R         S                                              ______________________________________                                        Grind base:                                                                   Chempol 11-1369 (g)                                                                          30.8      30.8      30.8                                       TiPure R-960 (g)                                                                             80.0      80.0      80.0                                       K-Flex 2302 Polyester                                                                        44.4      0.0        0.0                                       Resin (g)                                                                     K-Flex 2306 Polyester                                                                        0.0       45.7       0.0                                       Resin (g)                                                                     Chempol 11-1369 Polyester                                                                    0.0       0.0       38.5                                       Resin (g)                                                                     2,4,6-tris-(Butoxycarbonyl-                                                                  24.8      23.5      30.7                                       amino)-1,3,5-triazine (g)                                                     Para-Toluenesulfonic                                                                         0.4       0.4        0.4                                       Acid (g)                                                                      Substrate: Iron Phosphate-treated Cold Roll Steel (CRS)                       Coating performance                                                           Film thickness,                                                               (mils)         1.2       1.2        1.2                                       (mm)            0.030     0.030      0.030                                    Film hardness,                                                                KHN.sub.25     2.2       4.6       15.8                                       pencil         H-2H      H-2H      H-2H                                       Gloss, 20°/60°                                                                 73/89     86/94     82/94                                      Yellowness index                                                                             -3.3      -3.3      -3.8                                       MEK, rubs,                                                                    to mar         120       100       20                                         to remove      200+      200+      200+                                       Direct impact, in-lb                                                                         160+      160+      120                                        Reverse impact, in-lb                                                                        160+      160+      20                                         ______________________________________                                    

Although the present invention has been described with reference tocertain preferred embodiments, it is apparent that modifications andchanges thereof may be made by those skilled in the art, withoutdeparting from the scope of this invention as defined by the appendedclaims.

We claim:
 1. A method of coating a substrate comprising the steps of (a)contacting the substrate with a curable composition and, thereafter, (b)heat curing the curable composition, wherein the curable compositioncomprises:(a) a polyfunctional hydroxy group containing material; (b) anaminoresin crosslinking agent; (c) a co-crosslinking agent comprising a1,3,5-triazine-2,4,6-tris-carbamate of the formula C₃ N₃ (NHCOOR)₃ or anoligomer thereof; and (d) an acid cure catalyst,wherein the weight ratioof (a) to the sum of (b) and (c) is in the range of from 99:1 to 0.5:1,and wherein (d) is present in an amount of from 0.01 weight percent to 3weight percent based on the sum of (a), (b) and (c).
 2. The method ofclaim 1, wherein the co-crosslinking agent comprises a1,3,5-triazine-2,4,6-tris-carbamate of the formula C₃ N₃ (NHCOOR)₃,wherein R in each NHCOOR group is independently selected from the groupconsisting of an alkyl of 1 to 20 carbon atoms, an aryl of 6 to 20carbon atoms, and an aralkyl of 7 to 20 carbon atoms.
 3. The method ofclaim 2, wherein R in each NHCOOR group is independently selected froman alkyl of 1 to 8 carbon atoms.
 4. The method of claim 1, wherein theweight ratio of (b) to (c) is in the range of from 99:1 to 0.2:1.
 5. Themethod of claim 1, wherein the curable composition is a curable coatingcomposition comprising:(a) a hydroxyfunctional acrylic or polyesterresin; (b) an aminoresin crosslinking agent selected from the groupconsisting of N,N',N"-trialkoxymethyl melamine,N,N,N',N',N",N"-hexaalkoxymethyl melamine, N,N',N",N"',tetraalkoxymethyl glycoluril, oligomers thereof, and a mixture of any ofsaid aminoresin crosslinking agents; (c) a carbamate co-crosslinkingagent selected from the group consisting of2,4,6-tris-(methoxycarbonylamino)-1,3,5-triazine,2,4,6-tris-(butoxycarbonylamino)-1,3,5-triazine, and a mixture thereof;and (d) an acid cure catalyst selected from the group consisting of asulfonic acid, a dialkyl acid pyrophosphate, and a mixture thereof. 6.The method of claim 5, wherein the weight ratio of (b) to (c) is in therange of from 99:1 to 0.2:1.
 7. The method of claim 1, wherein thecurable composition is a curable coating composition comprising:(a) ahydroxyfunctional acrylic resin; (b) an N,N',N"-trimethoxymethylmelamine, an N,N,N',N',N",N"-hexamethoxymethyl melamine, oligomersthereof, and mixtures of said melamines; (c)2,4,6-tris-(butoxycarbonylamino)-1,3,5-triazine; and (d)para-toluenesulfonic acid, dimethyl acid pyrophosphate, or a mixturethereof.
 8. The method of claim 7, wherein the weight ratio of (b) to(c) is in the range of from 99:1 to 0.2:1.
 9. The method of claim 1,wherein the curable composition comprises a curable coating compositioncomprising:(a) a hydroxyfunctional acrylic resin; (b)N,N,N',N',N",N"-hexamethoxymethyl melamine; (c)2,4,6-tris-(butoxycarbonylamino)-1,3,5-triazine; and (d)para-toluenesulfonic acid.
 10. The method of claim 9, wherein the weightratio of (b) to (c) is in the range of from 99:1 to 0.2:1.
 11. Themethod of claim 1, wherein the 1,3,5-triazine-2,4,6-tris-carbamatecrosslinker is selected from the group consisting of2,4,6-tris-(methoxycarbonylamino)-1,3,5-triazine,2,4,6-tris-(butoxycarbonylamino)-1,3,5-triazine and a mixture thereof.12. The method of claim 11, wherein the1,3,5-triazine-2,4,6-tris-carbamate co-crosslinking is2,4,6-tris-(butoxycarbonylamino)-1,3,5-triazine.
 13. The method of claim1, wherein the polyfunctional hydroxy group containing material isselected from the group consisting of polyols, alkyds, hydroxyfunctionalacrylic resins, hydroxyfunctional polyester resins, hydroxyfunctionalpolyurethane prepolymers, products derived from condensation of epoxyresins with an amine, and a mixture thereof.
 14. The method of claim 13,wherein the polyfunctional hydroxy group containing material is ahydroxyfunctional acrylic or polyester resin.
 15. The method of claim 1,wherein the acid cure catalyst is selected from the group consisting ofa sulfonic acid, an alkyl or aryl acid phosphate or pyrophosphate, acarboxylic acid, a sulfonimide, a mineral acid, and a mixture thereof.16. The method of claim 15, wherein the acid cure catalyst is a sulfonicacid.
 17. The method of claim 1, wherein the aminoresin crosslinkingagent is selected from the group consisting of melamines, glycolurils,guanamines and ureas.
 18. The method of claim 1, wherein the aminoresincrosslinking agent is selected from the group consisting of:(I) analkoxymethyl melamine having two to six alkoxymethyl groups; (II) analkoxymethyl guanamine having two to four alkoxymethyl groups; (III) analkoxymethyl glycoluril having two to four alkoxymethyl groups; (IV) analkoxymethyl urea having two to four alkoxymethyl groups; (V) anoligomer of (I), (II), (III), or (IV); and (VI) a mixture of at leasttwo of any of (I), (II), (III), (IV) or (V).
 19. The method of claim 1,wherein the curable composition is in the form of a liquid, and is heatcured at a temperature in the range of from 90° C. to 140° C.
 20. Themethod of claim 1, wherein the curable composition is in the form of apowder, and is heat cured at a temperature in the range of from 175° C.to 190° C.